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Sonar Scholar

A high quality sonar system is likely to be one result of the awarding of the 1994 R.H.T. Bates Postgraduate Scholarship to Canterbury University PhD candidate David Hawkins.

Hawkins is working on developing a broad-band synthetic aperture sonar to produce high-resolution seafloor images. Using current non-synthetic-aperture sonar, the resolution of images tends to be limited to 10-20 square metre blocks. Hawkins hopes that his system will improve this to around one square metre, making it much more useful for finding small, artificial objects.

"You can then start locating things like mines, pipelines and sunken aircraft."

At present, he is building the sonar transmitter and receiver units, with the help of technical staff in the Electrical and Electronics Engineering Department. The units will undergo laboratory tests before being tested at sea. The initial sea trials will involve measuring the amount of transmitted energy that is reflected back to the receiver from seafloor environments, such as mud, sand and rock.

Due to the continuous nature of the transmitted signal, adaptive filters are required to track and remove the direct cross-talk between the transmitter and receiver, which tends to swamp the small signal from the seafloor. Once these small signals are recorded and corrections made to account for the sonar's movement, a synthetic aperture technique will be used to produce the final high-resolution images.